As is customary in the art, addition curing organopolysiloxane compositions comprising an organopolysiloxane containing silicon-bonded alkenyl groups and an organohydrogenpolysiloxane containing silicon-bonded hydrogen atoms (i.e., SiH groups) undergo addition reaction in the presence of a platinum based catalyst and cure into elastomers. A variety of such compositions are known.
The cured products of these compositions, however, are less adherent to metals and resins. When the compositions are used in such applications as potting and coating of electric circuits, impregnation of motor coils, impregnation of TV flyback transformers, bonding of semiconductor chips to circuit boards, bonding of structure joints, impregnation and coating of film or fabric form resins, there are drawbacks that peel often occurs and some necessary properties are lost.
From the past, efforts have been made to produce addition curing organopolysiloxane compositions that are fully adherent to many different substrates. For example, JP-B 53-13508 discloses an addition curing organopolysiloxane composition comprising a vinyl-containing diorganopolysiloxane, 100 to 1 part by weight of an epoxy and/or ester-containing organohydrogenpolysiloxane, and 0 to 99 parts by weight of an epoxy or ester-free organohydrogenpolysiloxane. JP-B 59-5219 discloses an addition curing organopolysiloxane composition comprising an organopolysiloxane containing trialkoxysilyl, oxirane and hydrosilyl groups on the molecule.
However, the bonding capability of these prior art addition curing organopolysiloxane compositions is insufficient as compared with other resin adhesive compositions like epoxy adhesive compositions. The bond retaining capability relative to metal, plastic and other substrates, and especially to plastic substrates is poor. It would be desirable to further improve a bonding capability.